Abstract
Blast waves from explosion sources such as a pressure vessel burst (PVB) exhibit both positive and negative phases, and the relative magnitude of the positive and negative phases is a function of standoff distance from the explosion source to the target of interest. When an incident blast wave reaches a target building, the blast wave will be reflected off the front wall (i.e., that facing the blast source). Both the blast wave positive and negative phases are affected by this reflection process. A fully reflected blast wave would be produced if the incident blast wave reflected off an infinitely tall and wide wall in a normal orientation. However, when an incident blast wave reflects from a facing wall of finite size, rarefaction waves are created at the edges of the wall and roof, which then sweep inward across the wall. The rarefaction waves result in a clearing effect for both the positive and negative phases. Clearing relieves some of the applied positive phase blast load on the reflected wall. However, clearing may either relieve or enhance the applied negative phase blast load, depending on the blast wave profile and the wall dimensions.
This paper focuses on the determination of negative phase clearing as a function of blast wave and structure parameters. Blast load adjustment factors (i.e., ratio of cleared to fully reflected blast loads) are introduced to characterize blast clearing as a function of these parameters. The purpose of the evaluation described in this paper was to generate a database of the blast clearing for engineering modeling of blast-structure interaction.
